Significant advancements in the field of lower leg prostheses have been made in recent years, due largely to the development of composite materials technology. Lower leg prostheses incorporating fiberglass/epoxy and carbon fiber/epoxy composite materials have been developed, which closely duplicate the performance characteristics and feel of the natural human foot and ankle.
One such lower leg prosthesis is sold by Otto Bock HealthCare, under the name Advantage Low Profile. That prosthesis incorporates a flexible lower member and a relatively rigid upper member, which are attached together by an intermediate elastomeric layer. A toe portion of the lower member projects beyond a forward end of the upper member, and a heel portion of the lower member projects beyond a rearward end of the upper member. The lower and upper members are formed of a high-strength, carbon fiber/epoxy composite material, and the intermediate layer is formed of a high-density polyurethane material. An attachment pyramid is mounted on the upper member, for attaching the lower leg prosthesis to a socket for receiving the amputee's residual limb or to an intermediate prosthetic component such as a pylon. A crepe or rubber sole can be attached to the underside of the lower member, and a foam foot shell or cosmesis can be placed over the members, to provide the prosthesis with an appearance of a natural human foot.
The Advantage Low Profile prosthesis described briefly above has enjoyed commercial success. Many other types of low profile lower leg prostheses are currently on the market, including the Otto Bock Luxon Max, Low Profile, and Luxon Journey. In addition, there are bssur's LP Vari-Flex® foot and Freedom Innovations' FS2000 LP (Low Profile) foot. Each of these lower profile foot prostheses has advantages and disadvantages. Nevertheless, it is believed that there is still a need for a foot prosthesis that provides greater stability during use, particularly at heel strike and at toe-off, and also provides greater smoothness throughout the transition from heel to toe, thus coming closer to duplicating the performance and feel of the natural human foot and ankle.